Transformer



July 17 1951 H. n. BRGWNELL 2,560,926

TRANSFORMER Filed June 1, 1949 H TT ORNE Y Patented Julyy 17, 1951 UNITED STATES PATENT OFFICE TRANSFORMER Harry Russell Brownell, New York, N. Y.

Application June 1, 1949, Serial No. 96,510

The present invention relates to transformers, more particularly to low voltage transformers where cost is a. major consideration and efllciency a minor one. Such transformers are particularly adapted for use in bell or chime circuits and can be used in larger sizes with toy electric trains, etc.

Low voltage transformers for use in home and building bell circuits must meet two major rerequirements. They must be as inexpensive as possible and operate within certain safety standards. They must be so constructed that a short in the secondary circuit will not cause a dangerous rise in current in the primary circuit and that overheating will not occur under usual or unusual conditions of operation.

Heretofore transformersof this type have been constructed of cores built up of a number of magnetizable metal laminations with primary and secondary coils wound on them. It has been necessary to stamp these laminations from sheet metal and then assemble and build them together to form a core of the thickness desired. The assembled core and coil has then been enclosed in a casing usually fashioned of two or three parts designed to iit together and cover all of the live or current-carrying parts.

This laminated core construction has proven quite efficient so that in order to limit the primary current to safe values on secondary short circuit it has been necessary either to build a high reactance into the transformer, thereby damping the effect of the secondary on the primary, or to include some type of overload switch or fuse in the primary which cuts out at dangerous current values. The addition of a thermostatic or overload switch is an appreciable cost, and a high reactance transformer of the laminated core type is relatively costly to manufacture because of the necessity of a larger core and generally larger design.

The present invention contemplates a transformer having a pair of members fitting together to act both as the core and casing of the transformer. These members may be made in any forms which may be adapted to perform this dual function. Preferablyat least one member comprises a substantially flat central portion, an outer flange and a central core of tongues protruding from the central portion. All of these are formed from a single sheet of metal in one shaping operation which strikes the tongues from the member, leaving apertures in the central portion which aid in cooling. Both members may be of this form but it may be desirable to 9 Claims. (Cl. 175-356) have one remain either a fiat cover or a cover with a flange or some other form approaching or similar to the first-mentioned member.

The flanges and tongues form an'annular cavity for the primary and secondary transformer coils, and the second member or cover closes the open end of the iirst member. The tongues of the central core pass through the coils to form a substantially closed magnetic circuit with the members. The members may possess solid portions in place of tongues to form a central core or may have a separate central core between them. A separate core piece may be included to fit with the tongues and increase the central flux path. The members, the core piece if included, and the coils can be held together by a simple bolt or rivet passing through all of them near the center of the unit.

This construction accomplishes tremendous cost savings over the conventional structure by eliminating the need for a separate casing, by the single operation formation of the combined lcasing and core members, and by the simple timesaving assembly and securing of these members with their internal parts to form an operable transformer. i

The present invention possesses a sufficiently high inherent reactance to assure that secondary short circuits will not cause the primary current to rise to unsafe values. On the other hand, the ratio of cooling surface to flux-carrying capacity in the combined core and casing is very high, so that this surface assisted by the tongue apertures provides adequate cooling under all conditions of operation. These characteristics made it unnecessary to build in an additional reactance or to add an overload switch to protect the primary circuit, thereby saving additional cost.

An obj ect of the present invention is to provide a less expensive low voltage transformer which will meet the safety requirements established for bell-ringing transformers for home use.

Another object of the invention is to eliminate the need for a separate transformer casing by the use of members which act both as core and casing.

Another object of the invention is to shape each core member in a single operation including the formation of any flanges or tongues or central core portions as may be used in a particular adaptation.

Another object of this invention is to provide a substantially closed magnetic circuit when the core members are placed together.

Another object of the invention is to provide a less expensive low voltage transformer whose parts can be simply assembled and secured together.

Another object of the invention is to provide a less expensive low voltage transformer with suflicient inherent reactance to prevent a short circuit in its secondary from creating dangerous primary currents, and at the same time possessing cooling characteristics adequate to prevent overheating. Another object of the invention is to provide, in a transformer, a combined core and casing, comprising a pair of interfltting members of the same shape.

A preferred embodiment of the invention has been chosen for purposes of illustration and descrlption and is shown in the accompanying drawings, wherein: n

Fig. 1 is an exploded view of one embodiment showing the interrelating transformer parts and their order of assembly;

Fig. 2 is a central sectional view of an assembled transformer of the first embodiment;

Fig. 3 is a side elevational view of the first embodiment; and

Fig. 4 is a plan view of a combined core and casing member of the second embodiment.

Referring to the embodiment illustrated in Figs. 1, 2 and 3. there is shown a circular magnetizable member I having a central portion 2 and a number of tongues 4 integral with said member and struck from the central portion so as to form an annular core about the center oi the member, the pattern of apertures 5 from which the tongues are struck being retained for cooling purposes. This central portion 2 has a flange 6 about its outer edge which with the tongues form an annular cavity adapted to receive the primary and secondary transformer coils 1. An insulating ring 3 is placed between the apertures 5 and the coils 1 to prevent contact with the live coils.

Fitting with the member I is the netizable member I2 having tongues I5 integral with said member and struck from the central portion to form an annular core around the center of the member, the pattern of apertures I6 from which the tongues were struck being retained for cooling purposes. The member I2 has a flange I1 about the outer edge of its central portion I4.

The flange I1 overlaps the flange 6 to close the open end of the member I and form a casing for the transformer. The tongues I5 overlap the tongues 4 and lt with them to form a central core which passes through the primary and secondary coils and establishes a substantially closed magnetic circuit with the two members. Thus the members I and I2 combine to act both as the core and the casing of the transformer.

'I'he insulating ring I8 ts between the primary and secondary coils 1 and the apertures I6 to prevent contact with the live coils. The hollow rivet I3 passes through the central portion 2 of the member I, the insulating ring 8, the primary and secondary coils 1, the insulating ring I8, and the central portion I4 of the member l2 to hold the members and `their parts firmly together.

The primary transformer leads 20 pass through the ports 2| and 22 in the member I, and the secondary leads (not shown) are connected to terminals 23 and 24through the holes 23a and 24a in member I2. The bracket member circular magwith a central portion Il 23 to be used in mounting the unit is secured 1s y advantages, it is to hollow rivet I9.

Referring to Figs. 1 and 2, there is a magnetizable core piece 21 in the form of a hollow roll of sheet material of helical cross section which can be included to lt Within the tongues 4 to provide a greater ilux path in the central core.

Referring to Fig. 4, another embodiment of this invention is shown in the combined core and casing member 23. This member has a central portion 28 with a flange 30 about its outer edge. This flange is divided into a plurality of sections illustrated herein as four and designated 3|, 32, 33 and 34, which are offset alternating inwardly and outwardly. The tongues 35 are struck from the central portion 29 to form an annular core of four offset sections 36, 31, 38 and 39 alternating inwardly and outwardly; the

apertures 40 formed by the tongues stamped therefrom serve for cooling purposes. The member 23 ts with a member of the same shape (not shown) so that the outwardly oiset flanges and tongues of one member overlap the inwardly offset ilanges and tongues of the other member. The holes 4| and 42 are used in one member for the primary leads and in the other for the secondary terminal connections. This embodiment has an advantage over the embodiment shown in Figs. l, 2 and 3 in that it allows both members to be shaped from the same die.

While the preferred embodiment has been described as a transformer it will be understood that the invention may be also utilized for reactive coils, "choke coils and the like.

It will be seen that the above invention provides a very simple and inexpensive transformer. The need for a separate casing has .been eliminated by two members combining the functions oi' core and casing. These two members can each be shaped in a single operation so that they iit together and contain an annular space adapted-to hold the transformer coils and insulating rings. The transformer can then be simply assembled by inserting a rivet or the like through these members with the transformer coils and insulating rings in place in this space. A substantially closed magnetic circuit is established between the central core comprising tongues of each member, the central portionsl of the members and the overlapping flanges.

Further, the relatively broad surfaces of the core members combine with the apertures in their central portions-to provide adequate cooling under the worst conditions of operation, while the inherent reactance of the unit is sufficient to prevent a short circuit in the secondary from creating dangerous primary current.

As various changes may be made in the form, construction and arrangements of the parts herein without departing from the spirit and scope of the invention and without sacrificing any of its bev understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. In a device of the class described, the combination of a magnetizable member having an end portion with a depending skirt adjacent an outer margin thereof and depending skirt means spaced inwardly from said outer depending skirtcomprlsing a plurality of depending tongues disposed apart from one another, said member having a plurality of cooling apertures in its end portion intermediate its skirt and skirt means, an addiaecomo tional magnetizable member at least partially nested within a space defined by said depending skirt, having an end portion with an upstanding skirt adjacent an outer margin thereof and upstanding skirt means spaced inwardly from said outer upstanding skirt comprising a plurality of upstanding tongues disposed apart from one another, said additional member having a plurality of cooling apertures in its end portion intermediate its skirt and skirt means, and means for retaining said members together whereby said end portions and outer margin skirts and inwardly spaced skirt means together define a coil receiving cavity.

2. In a device of the class described, the combination of a magnetizable metal member having an end portion with a depending skirt adjacent an outer margin thereof and depending core means spaced inwardly from said outer depending skirt comprising a plurality of depending tongues disposed apart from one another, said metal member being provided with cooling apertures in its end portion intermediate the depending skirt and core means, an additional magnetizable metal member fitting at least partially within said first mentioned member having an end portion with an upstanding skirt adjacent an outer margin thereof and upstanding core means spaced inwardly from said outer upstanding skirt comprising a plurality of upstanding tongues disposed apart from one another, said additional metal member being provided with cooling apertures in its end portion intermediate the upstanding skirt and core means, primary and secondary coils intermediate said end portions within said outer skirts and arranged around said core means, and insulating means intermediate said coils and each of said end portions.

3. In a device of the class described, the combination of a magnetizable casing member having an end portion with a depending skirt. adjacent an outer margin thereof, core means disposed inwardly from said skirt comprising a plurality of tongues depending from said end portion at spaced intervals, an additional magnetizable casing member in nested relationship with said first mentioned member having an end portion with an upstanding skirt adjacent an outer margin thereof, and core means disposed inwardly from said upstanding skirt comprising a plurality of tongues upstanding from the end p0rtion of the additional casing member at spaced intervals, each of said casing members being provided with apertures intermediate its skirt and its core means, and primary and secondary coils intermediate said end portions and within said .outer margin skirts and arranged around said core means.-

4. In a device of the class described the combination of a magnetizable casing member having an end portion with a depending skirt adjacent an outer margin thereof and depending skirt means disposed inwardly from said outer depending skirt comprising a plurality of tongues depending from said end portion at spaced intervals, and provided with apertures in its said end portion intermediate the depending skirt and skirt means, an additional magnetizable casing member adapted to fit partially within said first mentioned member having an end portion with 6 intervals and provided with apertures in its said end portion intermediate the upstanding skirt and skirt means, primary and secondary coils interan upstanding skirt adjacent an outer margin I mediate said end portions and intermediate one of said skirts and said skirt means and arranged around the skirt means, and core means intermediate said end portions and extending through said primary and secondary coils.

5. In a device of the class described the combination of a magnetizable member having an apertured end portion with a depending skirt adjacent an outer margin thereof, said skirt comprising oiiset sections alternating inwardly and outwardly, depending skirt means disposed inwardly from said outer depending skirt comprising a plurality of spaced tongues depending from said end portion and arranged in offset sections alternating inwardly and outwardly, an additional magnetizable member nested within said first mentioned member having an apertured end portion with an upstanding skirt adjacent an outer margin thereof, said skirt comprising offset sections alternating inwardly and outwardly, upstanding skirt means disposed inwardly from said outer upstanding skirt comprising a plurality of spaced tongues upstanding from said end portion and arranged in ofl'set sections alternating inwardly and outwardly, said outwardly offset sections and tongues of said additional member iitting over the inset sections and tongues of said first mentioned member and vice versa, and primary and secondary coils intermediate said end portions and intermediate one of said skirts and said skirt means with the coils arranged around the skirt means. y

6. A device as claimed in claim 3, in which said depending and upstanding skirts of the members have offset sections alternating inwardly and outwardly, with an outwardly offset section of the skirt of said iirst mentioned member fitting over an inset section of the skirt of said additional member, and vice versa.

7. A casing for a device of the class described comprising a pair of magnetizable members each including a cover means, the cover means of said members being spaced apart, skirt means projecting from the marginal portion of one of said cover means and terminating adjacent the other cover means, skirt means comprising a plurality of tongues projecting from a portion of one of said cover means spaced inwardly with respect to said marginal portion and terminating adjacent the other cover means, the cover means with said projecting tongues being provided with cooling apertures therethrough intermediate said marginal and inwardly spaced skirt means, and means retaining said members together whereby said spaced cover means and said marginal and inwardly spaced skirt means together define a coil receiving cavity.

8. A casing for a device of the class described comprising a pair of magnetizable members each including a cover means, the cover means of said members being spaced apart, skirt means projecting from the marginal portion of one of said cover means and terminating adjacent the other cover means, skirt means comprising a plurality of tongues projecting from a portion of each oi' said cover means spaced inwardly with respect to said marginal portion and terminating adjacent the other cover means, each of the cover means being provided with cooling apertures therethrough intermediate said marginal and inwardly spaced skirt means, and means retaining said members together whereby said spaced cover means and said marginal and inwardly spaced skirt means together define a coil receiving cavity.

9. A casing for a device of the class described comprising a pair oi' magnetizable members each including a cover means, the cover means of said members being spaced apart, skirt means projecting from the marginal portion of each of said cover means and each marginal skirt means terminating adjacent the other cover means, skirt means comprising a plurality of tongues projecting from a portion of each of said cover means spaced inwardly with respect to said marginal portion and each of said latter mentioned skirt means terminating adjacent the other cover means, each of the cover means being provided with cooling apertures therethrough extending from said inwardly spaced skirt means to a location adjacent said marginal skirt means, and

means retaining said members together whereby said spaced cover means and said marginal and inwardly spaced skirt means together deilne a coil receiving cavity.

HARRY 'RUSSELL BROWNELL.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS 

